定价： 819元 / 折扣价： 697 元

定价： 260元 / 折扣价： 221 元 加购物车

5.1 Measurements made by this test method are related to the night time brightness of retroreflective traffic signs approximately facing the driver of a mid-sized automobile equipped with tungsten filament headlights at about 100 m distance.5.2 Retroreflective material used on traffic signs degrades with time and requires periodic measurement to ensure that the performance of the retroflection provides adequate safety to the driver.5.3 The quality of the sign as to material used, age, and wear pattern will have an effect on the coefficient of retroreflection. These conditions need to be observed and noted by the user.5.4 This test method is not intended for use for the measurement of signs when the instrument entrance and observation angles differ from those specified herein.1.1 This test method covers measurement of the retroreflective properties of sign materials such as traffic signs and symbols (vertical surfaces) using a portable retroreflectometer that can be used in the field. The portable retroreflectometer is a hand-held instrument with a defined standard geometry that can be placed in contact with sign material to measure the retroreflection in a standard geometry. The measurements can be compared to minimum requirements to determine the need for replacement. Entrance and observation angles specified in this test method are those used currently in the United States and may differ from the angles used elsewhere in the world.1.2 This test method is intended to be used for the field measurement of traffic signs but may be used to measure the performance of materials before placing the sign in the field or before placing the sign material on the sign face.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车

5.1 This test method is a tool for quality assurance use. Given a pressure-sensitive label stock and a requirement in terms of the minimum or maximum peel adhesion value expected for this label stock, the data from the test can be used in conjunction with acceptance criteria.5.2 This test method can show the relative bond strength of a given label stock to one or more surfaces of varied material and texture as compared to the standard stainless steel panel. Substitution of panels representative of the proposed substrates for the standard stainless steel panel would be acceptable for this procedure.1.1 This test method covers the measurement of the peel adhesion of pressure-sensitive label stocks. This test method gives a measure of the adherence to a standard steel substrate or to other surfaces of interest for a pressure-sensitive label stock.1.2 This test method provides a means of assessing the uniformity of the adhesion of a given type of pressure-sensitive label stock. The assessment may be within a sheet or roll, between sheets or rolls, or between production lots.1.3 Variations in the label stock facestock and adhesive can affect the response; therefore, this test method cannot be used to pinpoint the specific cause(s) of nonuniformity.1.4 This test method may not be appropriate to test label stocks having either stiff backings or backings showing a high stretch at low forces. These characteristics could result in a high variability of the test response, which is not a true indication of the real nature of the adhesive bond.1.5 The values stated in either SI or inch-pound units are to be regarded separately as the standard. The values stated in each system may not be exact equivalents; therefore, each system must be used independently, without combining values in any way.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 515元 / 折扣价： 438 元 加购物车

This specification covers the material and fabrication of new reusable, slotted angle metal crates intended for use as containers for domestic and overseas shipment of lightweight airframe components and lightweight bulky items for domestic or overseas air and surface shipments. This specification includes metal crates in a variety of types, classes, and styles reflecting varied performance, but does not address their performance under al atmosphere, handling, shipping, and storage conditions. Type I are open crates, while Type II are fully-enclosed or sheathed with solid material. On the other hand, Class 1 are used for outside or indeterminate storage, while Class 2 are for inside or protected storage. And finally, Style A are furnished without skids or rubbing strips, while Style B are furnished with skid blocks or skids with rubbing strips and provisions for forklift truck handling. Details regarding the manufacture and construction requirements are itemized thoroughly.1.1 This specification covers the material and fabrication of new reusable metal (slotted angle) crates intended for use as containers for domestic and overseas shipment of lightweight airframe components and lightweight bulky items, not exceeding 3000 lb [1361 kg] for domestic or overseas air and surface shipments.1.2 Slotted angle crate performance is dependent on its fabricated components; therefore, a variety of types, classes, and styles reflecting varied performance are specified. This specification, however, does not cover slotted angle crate performance under all atmosphere, handling, shipping, and storage conditions.1.3 If the use of other construction methods or techniques are acceptable and permitted (see 5.1.12), the resulting packaging systems shall be of equal or better performance than would result from the use of these specified materials and procedures. The appropriate distribution cycle specified in Practice D4169 can be used to develop comparative procedures and criteria.1.4 The values stated in either inch-pound or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. See IEEE/ASTM SI 10 for conversion of units.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 646元 / 折扣价： 550 元 加购物车

5.1 Measurements made by this test method are related to the night time brightness of retroreflective traffic signs approximately facing the driver of a mid-sized automobile equipped with tungsten filament headlights at about 200 m distance.5.2 Retroreflective material used on traffic signs degrades with time and requires periodic measurement to ensure that the performance of the retroflection provides adequate safety to the driver.5.3 The quality of the sign as to material used, age, and wear pattern will have an effect on the coefficient of retroreflection. These conditions need to be observed and noted by the user.5.4 This test method is not intended for use for the measurement of signs when the instrument entrance and observation angles differ from those specified herein.1.1 This test method covers measurement of the retroreflective properties of sign materials such as traffic signs and symbols (vertical surfaces) using a portable retroreflectometer that can be used in the field. The portable retroreflectometer is a hand-held instrument with a defined standard geometry that can be placed in contact with sign material to measure the retroreflection in a standard geometry. The measurements can be compared to minimum requirements to determine the need for replacement. Entrance and observation angles specified in this test method are those used currently in the United States and may differ from the angles used elsewhere in the world.1.2 This test method is intended to be used for the field measurement of traffic signs but may be used to measure the performance of materials before placing the sign in the field or before placing the sign material on the sign face.1.3 This test method covers measurements at a 0.2 degree observation angle. See Test Method E2540 for measurements at a 0.5 degree observation angle.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车

4.1 Some tile surfaces may exhibit variations under low angle conditions as part of the designed aesthetic.4.2 This practice is intended for tiles that are designed to have an overall uniform appearance under low angle conditions.1.1 This practice replicates low angle viewing conditions on ceramic tile installations.1.2 The values stated in inch-pound units are to be regarded as the standard. The values in parentheses are for information only.1.3 This qualitative practice is intended to provide general guidance at the manufacturing level to determine if product will be acceptable under typical end use conditions.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 515元 / 折扣价： 438 元 加购物车

5.1 This test method is designed to show the adhesion of a pressure-sensitive tape to fiberboard when the tape is under a constant stress. Test data from this test method for some types of packaging tape relates to tape performance on fiberboard box closure.5.2 Procedure A should be used when comparing tapes to an established requirement. The requirement may be established using either the standard linerboard or another linerboard representing a specific fiberboard.5.3 Procedure B should be used to rank tapes as to their ability to adhere to fiberboard.1.1 This test method covers the determination of the property of adhesion of pressure-sensitive tape to a fiber-board surface. The user of this test method has the option of choosing the paper surface for the test. The test surface may be the standard linerboard, another linerboard (or paper) of individual interest, or a specific fiberboard.1.2 The values stated in either SI or inch-pound units are to be regarded separately as standard. The values stated in each system are not exact equivalents; therefore, each system must be used independently, without combining values in any way.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车

4.1 The degree of deacetylation of chitosan, as well at the molar mass and molar mass distribution, determines the functionality of chitosan in an application. For instance, functional and biological effects are highly dependent upon the composition and molar mass of the polymer.4.2 This test method describes procedures for measurement of molar mass of chitosan chlorides and glutamates, and chitosan base, although it in principle applies to any chitosan salt. The measured molar mass is that for chitosan acetate, since the mobile phase contains acetate as counter ion. This value can further be converted into the corresponding molar mass for the chitosan as a base, or the parent salt form (chloride or glutamate).4.3 Light scattering is one of very few methods available for the determination of absolute molar mass and structure, and it is applicable over the broadest range of molar masses of any method. Combining light scattering detection with size exclusion chromatography (SEC), which sorts molecules according to size, gives the ability to analyze polydisperse samples, as well as obtaining information on branching and molecular conformation. This means that both the number-average and mass-average values for molar mass and size may be obtained for most samples. Furthermore, one has the ability to calculate the distributions of the molar masses and sizes.4.4 Multi-angle laser light scattering (MALS) is a technique where measurements of scattered light are made simultaneously over a range of different angles. MALS detection can be used to obtain information on molecular size, since this parameter is determined by the angular variation of the scattered light. Molar mass may in principle be determined by detecting scattered light at a single low angle (LALLS). However, advantages with MALS as compared to LALLS are: (1) less noise at larger angles, (2) precision of measurements is improved by detecting at several angles, and (3) the ability to detect angular variation allows determination of size, branching, aggregation, and molecular conformation.4.5 Size exclusion chromatography uses columns, which are typically packed with polymer particles containing a network of uniform pores into which solute and solvent molecules can diffuse. While in the pores, molecules are effectively trapped and removed from the flow of the mobile phase. The average residence time in the pores depends upon the size of the solute molecules. Molecules that are larger than the average pore size of the packing are excluded and experience virtually no retention; these are eluted first, in the void volume of the column. Molecules, which may penetrate the pores will have a larger volume available for diffusion, they will be retained in the column for a time dependent upon their molecular size, with smaller molecules eluting after larger molecules.4.6 For polyelectrolytes, dialysis against the elution buffer has been suggested, in order to eliminate Donnan-type artifacts in the molar mass determination by light scattering (1, 2).5 However, in the present method, the size exclusion chromatography step preceding the light scatter detection is an efficient substitute for a dialysis step. The sample is separated on SEC columns with large excess of elution buffer for 30 to 40 min, and it is therefore in full equilibrium with the elution buffer when it reaches the MALS detector.1.1 This test method covers the determination of the molar mass of chitosan and chitosan salts intended for use in biomedical and pharmaceutical applications as well as in tissue engineered medical products (TEMPs) by size exclusion chromatography with multi-angle laser light scattering detection (SEC-MALS). A guide for the characterization of chitosan salts has been published as Guide F2103.1.2 Chitosan and chitosan salts used in TEMPs should be well characterized, including the molar mass and polydispersity (molar mass distribution) in order to ensure uniformity and correct functionality in the final product. This test method will assist end users in choosing the correct chitosan for their particular application. Chitosan may have utility as a scaffold or matrix material for TEMPs, in cell and tissue encapsulation applications, and in drug delivery formulations.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车

4.1 The composition and sequential structure of alginate, as well as the molar mass and molar mass distribution, determines the functionality of alginate in an application. For instance, the gelling properties of an alginate are highly dependent upon the composition and molar mass of the polymer.4.2 Light scattering is one of very few methods available for the determination of absolute molar mass and structure, and it is applicable over the broadest range of molar masses of any method. Combining light scattering detection with size exclusion chromatography (SEC), which sorts molecules according to size, gives the ability to analyze polydisperse samples, as well as to obtain information on branching and molecular conformation. This means that both the number-average and mass-average values for molar mass and size may be obtained for most samples. Furthermore, one has the ability to calculate the distributions of the molar masses and sizes.4.3 Multi-angle laser light scattering (MALS) is a technique where measurements are made simultaneously over a range of different angles and used to determine the scattering at 0°, which directly relates to molecular weight. MALS detection can be used to obtain information on molecular size, since this parameter is determined by the angular variation of the scattered light. This can be related to branching, aggregation, and molecular conformation. Molar mass can also be determined by detecting scattered light at a single low angle (LALS) and assuming that this is not significantly different from the scattering at 0°.4.4 Size exclusion chromatography uses columns, which are typically packed with polymer particles containing a network of uniform pores into which solute and solvent molecules can diffuse. While in the pores, molecules are effectively trapped and removed from the flow of the mobile phase. The average residence time in the pores depends upon the size of the solute molecules. Molecules that are larger than the average pore size of the packing are excluded and experience virtually no retention; these are eluted first, in the void volume of the column. Molecules which penetrate the pores will have a larger volume available for diffusion; their retention will depend on their molecular size, with the smaller molecules eluting last.4.5 For polyelectrolytes, dialysis against the elution buffer has been suggested, in order to eliminate Donnan-type artifacts in the molar mass determination by light scattering (1, 2).6 However, in the present method, the size exclusion chromatography step preceding the light scatter detection is an efficient substitute for a dialysis step. The sample is separated on SEC columns with large excess of elution buffer for 30 to 40 min, and it is therefore in full equilibrium with the elution buffer when it reaches the MALS detector.1.1 This test method covers the determination of the molar mass (typically expressed as grams/mole) of sodium alginate intended for use in biomedical and pharmaceutical applications as well as in tissue-engineered medical products (TEMPs) by size exclusion chromatography with multi-angle laser light scattering detection (SEC-MALS). A guide for the characterization of alginate has been published as Guide F2064.1.2 Alginate used in TEMPs should be well characterized, including the molar mass and polydispersity (molar mass distribution) in order to ensure uniformity and correct functionality in the final product. This test method will assist end users in choosing the correct alginate for their particular application. Alginate may have utility as a scaffold or matrix material for TEMPs, in cell and tissue encapsulation applications, and in drug delivery formulations.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

定价： 590元 / 折扣价： 502 元 加购物车

1.1 Particle size, shape, and bulk density will affect the flowability of powder material. This test method is used for the determination of the angle of repose of free-flowing mold powders. At angles greater than this value this material will flow.1.2 The values stated in inch-pound units and degrees are to be regarded as standard. The values stated in parentheses are for information only.1.3This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

定价： 0元 / 折扣价： 0 元

5.1 SGCs are used to produce asphalt mixture specimens in the laboratory to assess volumetric properties and predict pavement performance. In the fabrication of an SGC specimen in accordance with Test Method D6925, loose asphalt mixture is placed inside a metal mold, which is then placed into an SGC. A constant consolidation pressure is applied to the sample while the mold gyrates at a nominally constant angle (referred to as the internal angle of gyration) and rate. Consistency in the density of the asphalt specimens produced as measured by Test Method D2726/D2726M or D6752/D6752M is very important to the validity of the tests performed. Specimens of a consistent density are produced when an SGC maintains a constant pressure and a known constant internal angle of gyration during the compaction process.5.2 There are several manufacturers and models of SGC. Each model employs a unique method of setting, inducing, and maintaining the internal angle of gyration. Each model also employs a unique calibration system to measure the external angle of gyration. These existing calibration systems cannot be used universally on all of the different SGC models commercially available. Inconsistencies in asphalt specimens produced on different SGC models have been at least partially attributed to variations in the angle of gyration.5.3 This method describes instruments and processes that can be used to independently measure the internal angle of gyration of any manufacturer’s SGC model under simulated loading conditions. The external shape of the instrument chassis ensures that the points of physical contact between the mold end plates and the instrument occur at a fixed and known distance away from the axis of gyration. As a result, the vertical load is applied at these fixed points, creating tilting moments at each end of the mold.5.4 Unless otherwise specified, a tilting moment of 466.5 N-m shall be applied to the SGC by the instrument while making this measurement.NOTE 1: The quality of the results produced by this test method are dependent on the competence of the personnel performing the procedure and the capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of Specification D3666 are generally considered capable of competent and objective testing, sampling, inspection, etc. Users of this test method are cautioned that compliance with Specification D3666 alone does not completely ensure reliable results. Reliable results depend on many factors; following the suggestions of Specification D3666 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.NOTE 2: A 466.5 N-m tilting moment corresponds to a 22 mm eccentric on the AFLS1 or a 21° cone angle on the DAVII-HMS with an applied load of 10603 N (600 kPa at a 150 mm diameter specimen setting).1.1 This test method covers the procedure for the measurement of the Superpave Gyratory Compactor (SGC) internal angle of gyration using an instrument capable of simulating loading conditions similar to those created by an asphalt mixture specimen.1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. The value given in rotations per minute is provided for information regarding commonly used units.1.2.1 IEEE/ASTM SI 10, American National Standard for Metric Practice, offers guidance where use of decimal degrees for plane angles (versus radians) and revolutions per minute for rate of gyration (versus radians per second) is acceptable within the IEEE/ASTM SI 10 system when used on a minimal basis.1.3 The text of this test method references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车

5.1 This standard is useful for characterizing the wettability of surfaces. A surface that is easy to wet is one over which a coating is more likely to give good adhesion and appearance and less likely to suffer surface tension related defects such as crawling, cratering, pinholing and orange peel.5.2 This standard also can be used to test pigment surfaces for wettability, particularly by potential surfactant- or resin-based dispersants or mill bases. Easily wetted pigments are more likely to be easy to disperse and dispersants/mill bases that wet pigments of interest are more likely to disperse those pigments well.5.3 Although the contact angle is governed by the surface tensions of the test liquid and test surface, the angle cannot provide a surface tension value directly.5.4 A low advancing contact angle value (<45°) is indicative of wetting and angles of 10 to 20° are indicative of excellent wetting.5.5 Water can be used as a test liquid to establish (via the advancing contact angle) whether a surface is hydrophilic (angle <45°), hydrophobic (angle >90°) or somewhere in-between (angle of 45 to 90°). Water contact angles have been used to estimate surface cleanliness before and after cleaning operations, ease of wettability of surfaces by waterborne coatings and the effectiveness of rinsing processes.5.6 An organic liquid such as a solvent also can be used to characterize a substrate, coating or pigment. The resultant contact angle will depend on the surface tensions of the liquid and the test surface. A low surface tension (energy) test surface will not be wet by a high surface tension liquid.5.7 In addition to water and solvents, a surfactant dispersion or dispersant solution can be used to test a pigment surface. Any test liquid that is a potential dispersant for a test pigment must wet the pigment well or it will not work as a dispersant.5.8 Contact angle measurements can be used to map surfaces in terms of hydrophilicity, presence of low surface tension components or contaminants, or variations in composition. Other analytical methods such as infrared microscopy would be needed to identify the chemical moieties that give the contact angle differences.5.9 This test method can be used on nearly all coatings and substrates and may be extended to pigments by compressing the pigment powder into a solid disk.1.1 This practice covers the measurement of the angle of contact when a drop of liquid is applied to a coated surface, substrate, or preformed disk of pigment.1.2 There are two types of contact angles, advancing and receding. This standard deals only with advancing contact angles.1.3 This practice is intended to supplement the manufacturer’s instructions for the device being used to make the measurements, but is not intended to replace them.1.4 A common test liquid is water, but many other liquids such as solvents, surfactant and dispersant solutions and even liquid paints can be used.1.5 This practice is based on goniometry, which involves the observation of a sessile drop of test liquid on a solid substrate.1.6 Although contact angles are governed by surface tension, this standard cannot be used to measure surface tension directly.1.7 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 515元 / 折扣价： 438 元 加购物车

4.1 The rectangular or square copper alloy tube covered by this test method may be used in applications in which control of twist is important to proper fit in final assembly and to minimize rework to bring the tube into compliance. It is recognized that the amount of twist, in degrees per increment of length, can change as a result of the weight of the product and its length during measurement.4.2 This test method provides a procedure for measuring the twist in square and rectangular copper and copper alloy tubes as a measure of the deviation from straightness.4.3 This test method allows the purchaser and supplier or manufacturer to inspect square and rectangular copper and copper alloy tube with a standard technique that provides acceptable twist in delivered tubes.1.1 This test method establishes the requirements for the determination of the angle of twist in rectangular and square copper and copper alloy tube.1.2 The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 515元 / 折扣价： 438 元 加购物车

4.1 An electrical pulse is applied to a piezoelectric transducer which converts electrical to mechanical energy. In the angle-beam search unit, the piezoelectric element is generally a thickness expander which creates compressions and rarefactions. This longitudinal (compressional) wave travels through a wedge (generally a plastic). The angle between transducer face and the examination face of the wedge is equal to the angle between the normal (perpendicular) to the examination surface and the incident beam. Fig. 1 shows the incident angle φi, and the refracted angle φr, of the ultrasonic beam.FIG. 1 Refraction4.2 When the examination face of the angle-beam search unit is coupled to a material, ultrasonic waves may travel in the material. As shown in Fig. 2, the angle in the material (measured from the normal to the examination surface) and mode of vibration are dependent on the wedge angle, the ultrasonic velocity in the wedge, and the velocity of the wave in the examined material. When the material is thicker than a few wavelengths, the waves traveling in the material may be longitudinal and shear, shear alone, shear and Rayleigh, or Rayleigh alone. Total reflection may occur at the interface. (Refer to Fig. 3.) In thin materials (up to a few wavelengths thick), the waves from the angle-beam search unit traveling in the material may propagate in different Lamb wave modes.FIG. 2 Mode of VibrationFIG. 3 Effective Angles in the Steel versus Wedge Angles in Acrylic Plastic4.3 All ultrasonic modes of vibration may be used for angle-beam examination of material. The material forms and the probable flaw locations and orientations determine selection of beam directions and modes of vibration. The use of angle beams and the selection of the proper wave mode presuppose a knowledge of the geometry of the object; the probable location, size, orientation, and reflectivity of the expected flaws; and the laws of physics governing the propagation of ultrasonic waves. Characteristics of the examination system used and the ultrasonic properties of the material being examined must be known or determined. Some materials, because of unique microstructure, are difficult to examine using ultrasonics. Austenitic material, particularly weld material, is one example of this material condition. Caution should be exercised when establishing examination practices for these type materials. While examination may be possible, sensitivity will be inferior to that achievable on ferritic materials. When examining materials with unique microstructures, empirical testing should be performed to assure that the examination will achieve the desired sensitivity. This may be accomplished by incorporating known reflectors in a mock up of the weld or part to be examined. For material with such unique microstructures, a technique and procedure shall be agreed upon between contracting parties.4.3.1 Angle-Beam Longitudinal Waves—As shown in Fig. 4, angle-beam longitudinal waves with refracted angles in the range from 1 to 40° (where coexisting angle-beam shear waves are weak, as shown in Fig. 3) may be used to detect fatigue cracks in axles and shafts from the end by direct reflection or by corner reflection. As shown in Fig. 5, with a crossed-beam dual-transducer search unit configuration, angle-beam longitudinal waves may be used to measure thickness or to detect reflectors parallel to the examination surface, such as laminations. As shown in Fig. 6, reflectors with a major plane at an angle up to 40° with respect to the examination surface, provide optimum reflection to an angle-beam longitudinal wave that is normal to the plane of the reflector. Angle-beam longitudinal waves in the range from 45 to 85° become weaker as the angle increases; at the same time, the coexisting angle-beam shear waves become stronger. Equal amplitude angle beams of approximately 55° longitudinal wave and 29° shear wave will coexist in the material, as shown in Fig. 7. Confusion created by two beams traveling at different angles and at different velocities has limited use of this range of angle beams.FIG. 4 AxleFIG. 5 ThicknessFIG. 6 Angle LongitudinalFIG. 7 Coincident Beams4.3.2 Angle-Beam Shear Waves (Transverse Waves)—Angle-beam shear waves in the range from 40 to 75° are the most used angle beams. They will detect imperfections in materials by corner reflection and reradiation (as shown in Fig. 8) if the plane of the reflector is perpendicular to a material surface, and by direct reflection if the ultrasonic beam is normal to the plane of the reflector (as shown in Fig. 9). Reflectors parallel to the examination surface (such as laminations in plate, as shown in Fig. 10) can rarely be detected by an angle beam unless accompanied by another reflector; for example, a lamination at the edge of a plate (as shown in Fig. 11) can be detected by corner reflection from the lamination and plate edge. Generally, laminations should be detected and evaluated by the straight-beam technique. Angle-beam shear waves applied to weld testing will detect incomplete penetration (as shown in Fig. 12) by corner reflection, incomplete fusion (as shown in Fig. 13) by direct reflection (when the beam angle is chosen to be normal to the plane of the weld preparation), slag inclusion by cylindrical reflection (as shown in Fig. 14), porosity by spherical reflection, and cracks (as shown in Fig. 15) by direct or corner reflection, depending on their orientation. Angle-beam shear waves of 80 to 85° are frequently accompanied by a Rayleigh wave traveling on the surface. Confusion created by two beams at slightly different angles, traveling at different velocities, has limited applications in this range of angle beams.FIG. 8 CornerFIG. 9 Normal PlaneFIG. 10 LaminarFIG. 11 Edge LaminationFIG. 12 Incomplete PenetrationFIG. 13 Incomplete FusionFIG. 14 Slag and PorosityFIG. 15 Cracks4.3.3 Surface-Beam Rayleigh Waves—Surface-beam Rayleigh waves travel at 90° to the normal of the examination surface on the examination surface. In material greater than two wavelengths thick, the energy of the Rayleigh wave penetrates to a depth of approximately one wavelength; but, due to the exponential distribution of the energy, one half of the energy is within one-quarter wavelength of the surface. Surface cracks with length perpendicular to the Rayleigh wave can be detected and their depth evaluated by changing the frequency of the Rayleigh wave, thus changing its wavelength and depth of penetration. Wavelength equals velocity divided by frequency.Subsurface reflectors may be detected by Rayleigh waves if they lie within one wavelength of the surface.4.3.4 Lamb Waves—Lamb waves travel at 90° to the normal of the test surface and fill thin materials with elliptical particle vibrations. These vibrations occur in various numbers of layers and travel at velocities varying from slower than Rayleigh up to nearly longitudinal wave velocity, depending on material thickness and examination frequency. Asymmetrical-type Lamb waves have an odd number of elliptical layers of vibration, while symmetrical-type Lamb waves have an even number of elliptical layers of vibration. Lamb waves are most useful in materials up to five wavelengths thick (based on Rayleigh wave velocity in a thick specimen of the same material). They will detect surface imperfections on both the examination and opposite surfaces. Centrally located laminations are best detected with the first or second mode asymmetrical Lamb waves (one or three elliptical layers). Small thickness changes are best detected with the third or higher mode symmetrical or asymmetrical-type Lamb waves (five or more elliptical layers). A change in plate thickness causes a change of vibrational mode just as a lamination causes a mode change. The mode conversion is imperfect and may produce indications at the leading and the trailing edges of the lamination or the thin area.1.1 This practice covers ultrasonic examination of materials by the pulse-echo technique, using continuous coupling of angular incident ultrasonic vibrations.1.2 This practice shall be applicable to development of an examination procedure agreed upon by the users of the practice.1.3 The values stated in inch-pound units are regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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